migration/savevm.c: migrate non-default page size
Add a subsection to vmstate_configuration which is present
only if the guest is using a target page size which is
different from the default. This allows us to helpfully
diagnose attempts to migrate between machines which
are using different target page sizes.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
diff --git a/migration/savevm.c b/migration/savevm.c
index a831ec2..cfcbbd0 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -265,6 +265,7 @@
bool skip_configuration;
uint32_t len;
const char *name;
+ uint32_t target_page_bits;
} SaveState;
static SaveState savevm_state = {
@@ -286,6 +287,19 @@
state->len = strlen(current_name);
state->name = current_name;
+ state->target_page_bits = TARGET_PAGE_BITS;
+}
+
+static int configuration_pre_load(void *opaque)
+{
+ SaveState *state = opaque;
+
+ /* If there is no target-page-bits subsection it means the source
+ * predates the variable-target-page-bits support and is using the
+ * minimum possible value for this CPU.
+ */
+ state->target_page_bits = TARGET_PAGE_BITS_MIN;
+ return 0;
}
static int configuration_post_load(void *opaque, int version_id)
@@ -298,12 +312,43 @@
(int) state->len, state->name, current_name);
return -EINVAL;
}
+
+ if (state->target_page_bits != TARGET_PAGE_BITS) {
+ error_report("Received TARGET_PAGE_BITS is %d but local is %d",
+ state->target_page_bits, TARGET_PAGE_BITS);
+ return -EINVAL;
+ }
+
return 0;
}
+/* The target-page-bits subsection is present only if the
+ * target page size is not the same as the default (ie the
+ * minimum page size for a variable-page-size guest CPU).
+ * If it is present then it contains the actual target page
+ * bits for the machine, and migration will fail if the
+ * two ends don't agree about it.
+ */
+static bool vmstate_target_page_bits_needed(void *opaque)
+{
+ return TARGET_PAGE_BITS > TARGET_PAGE_BITS_MIN;
+}
+
+static const VMStateDescription vmstate_target_page_bits = {
+ .name = "configuration/target-page-bits",
+ .version_id = 1,
+ .minimum_version_id = 1,
+ .needed = vmstate_target_page_bits_needed,
+ .fields = (VMStateField[]) {
+ VMSTATE_UINT32(target_page_bits, SaveState),
+ VMSTATE_END_OF_LIST()
+ }
+};
+
static const VMStateDescription vmstate_configuration = {
.name = "configuration",
.version_id = 1,
+ .pre_load = configuration_pre_load,
.post_load = configuration_post_load,
.pre_save = configuration_pre_save,
.fields = (VMStateField[]) {
@@ -311,6 +356,10 @@
VMSTATE_VBUFFER_ALLOC_UINT32(name, SaveState, 0, NULL, 0, len),
VMSTATE_END_OF_LIST()
},
+ .subsections = (const VMStateDescription*[]) {
+ &vmstate_target_page_bits,
+ NULL
+ }
};
static void dump_vmstate_vmsd(FILE *out_file,
